1. Field of the Invention
Embodiments of the present invention relate to axle support structures for industrial vehicles such as a forklift.
2. Description of the Related Art
A counterbalance type forklift has a machine base frame as a vehicle body member. The machine base frame is a rear frame of a machine frame. The machine base frame supports a rear axle so that the rear axle can swing within a roll plane. This helps to achieve an improvement in terms of a stability of the vehicle during traveling on a road surface that is not flat. FIG. 15 is a sectional view illustrating an industrial vehicle axle support structure.
As shown in FIG. 15, a machine base frame 150 is provided with front and rear axle supports 151 and 152 arranged in the longitudinal direction (the horizontal direction as seen in FIG. 15). The two axle supports 151 and 152 respectively have support holes 156 and 157. The axle supports 151 and 152 are of a divisional structure divided into two portions above and below the support holes 156 and 157. The axle supports 151 and 152 respectively include upper support members 151a and 152a and lower support members 151b and 152b. The upper support members 151a and 152a are fixed to the machine base frame 150 by welding or the like. The lower support members 151b and 152b are detachably mounted to the upper support members 151a and 152a by bolt means. The bolt means include headed bolts 160 and screw holes (not shown) provided in the upper support members 151a and 152a. The bolts 160 threadedly engage with the screw holes. A rear axle 153 is arranged between the axle supports 151 and 152. Front and rear center pins 154 and 155 are respectively provided on front and rear surfaces of the rear axle 153. The center pins 154 and 155 are respectively rotatably supported within the support holes 156 and 157 of the axle supports 151 and 152.
When the rear axle 153 is to be mounted to the machine base frame 150, the lower support members 151b and 152b are removed from the upper support members 151a and 152a. The center pins 154 and 155 of the rear axle 153 are arranged in the upper halves of the support holes 156 and 157 of the upper support members 151a and 152a. The lower support members 151b and 152b are respectively fastened to the upper support members 151a and 152a by the bolts 160. As a result, the lower halves of the center pins 154 and 155 are supported within the lower halves of the support holes 156 and 157. A bush 162 serving as a bearing is provided between each center pin 154, 155 and each inner surface of the support hole 156, 157. A detachment prevention plate 163 is fixed to one support member of each axle support 151, 152 by welding or the like. For example, the detachment prevention plate 163 is fixed to the lower support member 151b of the front axle support 151, and to the upper support member 152a of the rear axle support 152. Each detachment prevention plate 163 prevents the bush 162 from passing through the support hole 156, 157 to the side opposite the rear axle 153. A grease nipple (not shown) is attached to each upper support member 151a, 152a. 
There may be dimensional variation in the machine base frame 150 and the rear axle 153. A clearance C for canceling effect of said variation is set between the axle support 151 or 152 and the rear axle 153. Thus, despite said variation, the rear axle 153 can be mounted between the axle supports 151 and 152. The clearance C may allow the rear axle 153 to rattle in the vehicle longitudinal direction. To prevent this rattling, the rear axle 153 is brought close, for example, to the front axle support 151. Shims 158 are arranged in the clearance C between the rear axle support 152 and the rear axle 153. The number of shims 158 is selected in response to the clearance C. Alternatively, a shim 158 of a thickness is selected in response to the clearance C.
Japanese Laid-Open Patent Publication No. 2000-16039 discloses an axle support structure having front and rear axle supports. Each axle support is of a vertically divisional structure. The each axle support has an upper support member fixed to a machine base frame, and a lower support member detachably attached to the upper support member.
The axle support structure has the detachment prevention plate 163. The prevention plate 163 is welded to each of the support members 151b and 152a. Thus, the number of components of the axle support structure is rather large. And a lot of production man-hours are involved. The axle is applicable not only to a forklift but also to various industrial vehicles such as a tractor shovel, a shovel loader, and a towing tractor. The various industrial vehicles have the axle swingably supported by a machine base frame.
Therefore, there is a need in the art for an axle support structure involving a smaller number of components and less production man-hours.